RIDE FASTER AND LONGER: IMPROVE YOUR DRIVETRAIN EFFICIENCY

Some simple gear tweaks and maintenance jobs will save you wattage, leading to faster, longer riding.

Regular training and a good diet will not only pay dividends with your health and fitness, but also the efficiency of your equipment, specifically the drivetrain. That’s because frictional losses become a smaller part of total input power the faster you ride. For instance, hold an average between 200-300w and peak drivetrain efficiency measures around 96-97.5%. Above 300w and you’re looking at a peak of 97-98%.

Note that these figures are at the top end. A landmark study by Dr James Spicer in 2000 showed that drivetrain efficiency varied significantly, from 80.9% to 98.6% depending on the conditions of the drive operation. Technology has moved on since 2000, but the core principles are exactly the same. Spicer demonstrated that the primary factors affecting efficiency included the size of the sprockets in the drive and the tension in the chain, but other research has also shown the benefits of quality equipment and lubrication. It’s time to ride the road of least resistance.

Sprocket combinationsSpicer and many of his contemporaries have proved that larger sprockets are more efficient at transferring power. In the case of Spicer’s experiments, a 52-11-tooth set-up, cycling at 175w, had an efficiency rating of 95.5%. That figure rose to 98.2% when using 52-21t. Why the discrepancy? It’s primarily down to the less extreme radius of rotation, so remember: if you can generate the same power using a large chainring and large-sprocket combination compared to a small chainring/small-sprocket combination, go large. Here’s some background reading.

ChainThe power savings from the chain are the greatest you can make losses of around 7-10watts of energy due to friction. That’s the bad news. The good news is it’s the easiest component to reel in those lost watts. At a basic level, simply wiping and lubing your chain before each ride can cut losses by an incredible 5w. As a reference point, 1w equates to around a 30-seconds saving over a 112-mile bike ride. So if you are going long and hitting that 112 figure, you’ll save a mind-boggling 2:30mins. Which lube you use also impacts on performance. While all achieve the similar role of filling the gaps in the links that’d normally be filled by grime and dirt, lower-viscosity lubes have proven to be more efficient – far more efficient than factory lube that’s used on the bike as that might be designed for durability more than pace. Read our feature on regular chain mantenance and see the video here.

Chain tensionTension of the chain also impacts efficiency. Again drawing on the work of Spicer, he showed that higher chain tension was more efficient than lower tension. More specifically, 98.6% efficiency was measured at a chain tension of 305N compared to just 80.9% at 76.2N tension. It’s another reason why a large plus large chainring/sprocket combination is more efficient than a small/small when generating the same power output.

You’d be forgiven for thinking therefore that new chains would the most efficient as they have less ‘give’ in them, but think again. Research shows that chains that have been run-in slightly are the most efficient, gains improving as the first few hours roll by. So if you are buying a new chain for your goal race, warm it up for a few hours in the build-up week to save another 0.5w.

BB and derailleursThe bearings in your bottom bracket can also cost you a further 6-8w in energy. Ceramic bearings are proven to run with less friction but simply greasing the BB on a regular basis can ensure similar savings, as well as increasing the component’s longevity. You should also play around with your derailleurs. Swap out your parochial pulleys that feature simple bushings with good-quality versions that feature steel bearings. A further 1.5% saving has been measured with this basic change.

The principles we’ve explored apply across all chains – 9, 10 and 11-speed systems and are relatively easy to apply to great, ongoing gains – now go and ride!